A communication apparatus for railway carriages that has conventionally been known includes: a configuration controlling unit having an interface that uses a carrier sense multiple access method; a switching hub that branches a transmission path; and a switch that disconnects input/output signals to and from the switching hub. The communication apparatus makes it possible to recognize a configuration of a train by controlling communications in upstream and downstream directions of the transmission path by connecting and disconnecting the switch (e.g., Patent Document 1 listed below).
In the communication apparatus for railway carriages described in Patent Document 1, failures are avoided by using the switching hub that configures communication apparatuses so as to have one-to-one communications. In addition, no master communication apparatus is provided so that it is possible to prevent communication halts within the carriages and to improve the reliability of the system.    Patent Document 1: Japanese Patent Application Laid-Open No. 2005-117373